Enhancement of Word-Recognition Performance With a Filtering Technique
Richard H. Wilson, John P. Preece, Court S. Crowther · Journal of Speech Language and Hearing Research · 1991
The NU No. 6 materials spoken by a female speaker were passed through a notch filter centered at 247 Hz with a 34-dB depth. The filtering reduced the amplitude range within the spectrum of the materials by 10 dB that was reflected as a 7.5-vu reduction measured on a true vu meter. Thus, the notch filtering in effect changed the level calibration of the materials. Psychometric functions of the NU No. 6 materials filtered and unfiltered in 60-dB SPL broadband noise were obtained from 12 listeners with normal hearing. Although the slopes of the functions for the two conditions were the same, the functions were displaced by an average of 5.8 dB with the function for the filtered materials located at the lower sound-pressure levels.